- BritGrav 15April was a busy month. Amongst other adventures, I organised the 15th British Gravity (BritGrav) Meeting. This is a conference for everyone involved with research connected to gravitation. I was involved in organising last year's meeting in Cambridge, and since there were very few fatalities, it was decided that I could be trusted to organise...
- First up, Chris Collins talks is about testing gravity with the Inverse Square Law experiment. #BritGrav15
- The search for Newton's constantThree decades of careful experimentation have painted a surprisingly hazy picture of the constant governing the most familiar force on Earth.
- Haoyu Wang talks about talks about reducing thermal noise in Advanced LIGO #BritGrav15
- Space Time QuestDaniel Brown Paul Fulda Ludovico Carbone 2010 Have you ever wondered what it would be like to be in charge of a budget of £100 Million!? Have you ever wondered what it would be like to be the principal investigator on a continent spanning science project, with the aim of making one of the most important discoveries of the last 50 years!?
- Josh Freedman on his masters' project modelling laser beam modes for Advanced LIGO #BritGrav15
- Duncan Meacher on a mock data challenge for the Einstein Telescope, a future gravitational-wave detector. #BritGrav15
- Einstein Telescopeadministrator The ET (Einstein Telescope) project aims to the realization of a crucial research infrastructure in Europe: a third generation Gravitational Wave observatory. ET has been supported as Design Study by thehis phase is concluded and a Conceptual European Commission under the Framework Programme 7 ( Design Document has been released; currently a new phase is open focused on the needed technologies development.
- Meacher: ET detections out to max of z ~ 2. #BritGrav15
- Yiming Hu explains how we can be confident that we have actually made a gravitational-wave detection. #BritGrav15
- Hu: estimating noise background noise in LIGO difficult as we can't shield detectors from signals. Need network of detectors. #BritGrav15
- Alex Nielsen on detecting neutron star-black hole binaries with Advanced LIGO #BritGrav15
- Scientists: Collision of dead stars produced the world's gold - CNN.comAll that glitters is not gold, they say. But all the gold in the world may come from astronomical events that send a lot of high-energy light out in space. Researchers have new evidence that gold comes from the collision of neutron stars.
- Christopher Berry @cplberry talks about binary neutron stars measurements with Advanced LIGO #BritGrav15
- .@cplberry Chirp mass measured well even without spin. Sky area hundreds of square degrees http://arxiv.org/abs/1411.6934
- The First Two Years of Electromagnetic Follow-Up with Advanced LIGO and VirgoCatalog of simulated events and sky maps for two-detector, HL, 2015 configuration. This is the same configuration as the 2015, recoloured tab, except that the simulated detector noise is Gaussian. See also ASCII tables of simulated signals, detections, and parameter-estimation accuracies in Machine Readable Table format.
- Will Vousden @willvousden on speeding up parameter estimation with parallel tempering of MCMC: use a dynamical chain #BritGrav15
- .@willvousden: Dynamical chain gives a factor of a few improvement http://arxiv.org/abs/1501.05823 In process of testing for LIGO data. #BritGrav15
- Chris Moore on how to overcome uncertainty in waveform templates for Advanced LIGO parameter estimation. #BritGrav15
- Jade Poxwell @JadePowell12 on using gravitational waves to learn about supernovae collapse #BritGrav15
- .@JadePowell12 Uncertainty in supernovae waveforms. New paper on results this summer! #BritGrav15
- @BritGrav15 I'm not looking at uncertainty in the waveforms just using them to find explosion mechanism :-)
- Simon Stevenson @simon4nine talks about understanding the astrophysics of binaries: important for understanding gravitational waves
- Distinguishing population synthesis models using gravitational waves http://arxiv.org/abs/1504.07802 by @simon4nine, Ohme & Fairhurst
- .@simon4nine Including spin precession of black holes adds info to waveform. It is an imprint of binary evolution #BritGrav15
- Could you tell direct collapse black holes from those via neutron star collapse? @simon4nine: Maybe via natal kick. #BritGrav15
- Hannah Middleton on using pulsar timing arrays to detect background of background gravitational waves from massive black holes #BritGrav15
- Middleton: What can a PTA upper limit tells us about black hole population? Not much about anything other than number density. #BritGrav15
- Middleton: Detection is more constraining! Frequency dependence could help constrain more physics. #BritGrav15
## Session 3 (Chair: Hannah Middleton)

- Davide Gerosa on the most massive black holes in the Universe. Increase by a factor of 2 in mass since z = 2 by mergers #BritGrav15
- Gerosa: Undermassive BHs in BCGs indicates a larger number of mergers. A missing BH means a superkick from merger http://arxiv.org/abs/1405.2072
- Maggie Lieu @Space_Mog on weak lensing mass measurement of galaxy clusters, a useful probe for cosmology #BritGrav15
- .@Space_Mog: Use hierarchical modelling to describe population! Thanks @farrwill. Few assumptions & can include selection effects.
- Mateja Gosenca on general relativistic N-body simulations. Important for testing GR or including relativistic perturbations #BritGrav15
- Viraj Sanghai on constricting a post-Newtonian cosmological models #BritGrav15
- Sanghai: Obtain Friedmann-like equations. More details in http://arxiv.org/abs/1503.08747 #BritGrav15
- Gregory Ashton on periodic variability (timing noise) in pulsars. Precession or beam switching? #BritGrav15
- Vanessa Graber on the magnetic fields of neutron stars. Magnetars have fields of 10^15 G! #BritGrav15
- Graber: Need to consider vortex-flux tube interactions to get larger friction and shorter evolution timescale. #BritGrav15
- Graber: Large number of flux tubes (10^18 cm^-2) allows averaging for macroscopic properties. #BritGrav15
- Alice Harpole discusses type I X-ray bursts: explosive fusion in ocean of accreted material on neutron star #BritGrav15
- Harpole: Strong-gravity effects likely to be important, need to include in simulations. Can use low-Mach approximation #BritGrav15
- Harpole: Simulation http://www.southampton.ac.uk/~ah1e14/ only took 5 min on desktop using approximation! #BritGrav15
- Konstantinos Palapanidis on the inside of neutron stars. Strong interaction between proton and neutron fluids. #BritGrav15
## Session 4 (Chair: Maggie Lieu)

- Weyl tensorIn differential geometry, the Weyl curvature tensor, named after Hermann Weyl, is a measure of the curvature of spacetime or, more generally, a pseudo-Riemannian manifold. Like the Riemann curvature tensor, the Weyl tensor expresses the tidal force that a body feels when moving along a geodesic.
- Jarrod Williams on the constant equations for numerical relativity calculations. These describe initial conditions #BritGrav15
- Gernot Heißel also on initial data. Current codes use wormhole data for black holes. These evolve to trumpets: start there! #BritGrav15
- Heißel: Presenting numerical derivation for Schwarzschild trumpet data as a guideline for Kerr. Matches analytical solution. #BritGrav15
- Heißel: Hopefully have Kerr initial trumpet data for next BritGrav! #BritGrav16
- William Cook on gravitational waves in higher dimensions. Simulations done in 5D. Building on that with new formalism. #BritGrav15
- Sebastian Khan on new gravitational waveform with inspiral, merger and ringdown plus precession! #BritGrav15
- Khan: PhenomD is frequency domain (fast). Calibrated against more waveforms. All matches better than 0.98! #BritGrav15
- Khan: PhenomD beats SEOBNR for large spins and high mass ratio. #BritGrav15
- Looking forward to PhenomD ! @NoWorkWednesday @BritGrav15
## Session 5 (Chair: Chris Collins)

- To start off, Tedora Oniga on gravitational decoherence, which is still not well understood. #BritGrav15
- Spurgeon Talaganis on understanding loops in higher derivative gravity #BritGrav15
- Lisa Glaser on Hartle Hawking wave function in causal set quantum gravity. A lot for 10 min, she's going to speak quickly! #BritGrav15
- Jos Gibbons is talking about massless scalar fields, which he promises are really relevant for a gravitational conference #BritGrav15
- Gibbons: de Sitter space is interesting because of symmetry and because the universe is falling up (accelerating) #LittleBritGrav
- Gibbons: More details in our paper http://arxiv.org/abs/1410.7830 Still working on gravity calculations #BritGrav15
- Ilia Musco will give us the latest results regarding quasi-static solutions for compact objects in Chameleon models #BritGrav15
- Musco: Chameleon mechanism screens scalar fields so it can explain dark energy and evade local measurements. #BritGrav15
- Musco: Universal solution for incompressible star, central scalar field depends on compactness M/R and coupling strength #BritGrav15
- Mattia Colombo on Horava gravity. Results in http://arxiv.org/abs/1410.6360 and http://arxiv.org/abs/1503.07544 #BritGrav15
- Aindriú Conroy explains the Raychaudhuri equation before what it means to be geodesic incomplete. #BritGrav15
## Session 6 (Chair: Will Farr)

- Christian Luebbe on conformal cyclic cosmologies (CCC). He'll be using conformal scalar fields. #BritGrav15
- Luebbe: Can use conformal scalar field (CSF) to map aeons. Does CSF control inflation? Are there applications in AdS/CFT? #BritGrav15
- Leithes: For 1st time, evolution of stable perturbations in 2 fluid, 2 field, sum of exps model. Papers for PYESSENCE soon #BritGrav15
- Adam Christopherson @AJChristo is interested in axions, a potential candidate for dark matter. #BritGrav15
- .@AJChristo: Modelling axion as a classical field with Schroedinger-Poisson equations. This reproduces homogeneous background. #BritGrav15
- .@AJChristo: Need inhomogeneities for structure formation. Linear Newtonian perturbations reproduced from Schroedinger-Poisson equations!
- Linear Newtonian perturbation theory from the Schrödinger-Poisson equations by Banik @AJChristo Sikivie & Todarello http://arxiv.org/abs/1504.05968
- Brien Nolan is going to tell us about his favourite spacetime: McVittie (embedding of Schwarzschild in FRW) #BritGrav15
- Nolan: Class 1, with cosmological constant: can extend across r = 2m to Schwarzschild-de Sitter. More like a black hole! #BritGrav15
- Nolan: Does black hole or expansion win? Depends where you are, stable orbits are possible. #BritGrav15
- Matthew Wright on a solution for slowly rotating perfect fluids with a cosmological constant http://arxiv.org/abs/1411.5486 #BritGrav15
- Edgar Gasperín on conformal geometry. Analysing extremal Swarzschild-de Sitter #BritGrav15
- Michael Cole will be telling us about Killing spinors. Killing spinors tell us about properites (Petrov type) of spacetime #BritGrav15
- Cole: In electrovacuum, trying to find Killing spinor. Could evolve integrability condition with suitable initial conditions #BritGrav15
- Cesar Merlin wants to find extreme mass-ratio inspiral gravitational waveforms http://arxiv.org/abs/1310.1513 http://arxiv.org/abs/1410.2998 #BritGrav15
## Session 7 (Chair: Simon Stevenson)

- David Dempsey on the bound states of the Dirac equation in Kerr http://arxiv.org/abs/1504.03190 A black hole hydrogen atom #BritGrav15
- Dempsey: Tested analytic results and found new features at critical frequency. Next, looking at hyperfine structure. #BritGrav15
- Dempsey: Tested analytic results and found new features at critical frequency. Next, looking at hyperfine structure. #BritGrav15
- Vladimir Toussaint on a particle detector in a cylindrical spacetime where there is no privileged vacuum state. #BritGrav15
- Toussaint: Simplest detector: a 2-level quantum system. Can distinguish two spin structures by zero mode. #BritGrav15
- Benito Juárez-Aubry is going to talk about quantum effects at a Cauchy Horizon, but not Gandalf. #BritGrav15
- Juárez-Aubry: Respect causality and don't do near a Cauchy horizon! #BritGrav15
- Hugo Ferreira wants to calculate local observables for a rotating black hole background (using a quasi-Euclidean method). #BritGrav15
- Supakchai Ponglertsakul is looking at black hole solutions in Einstein-charged scalar field theory. #BritGrav15
- Ponglertsakul: What could be the end point of instabilities? Hairy black holes found numerically. These seem stable. #BritGrav15
- Yafet Sánchez Sánchez: general relativity predicts its own breakdown through the presence of singularities. #BritGrav15
- Bernard Kay on black holes in a box (not an astrophysical black hole… ) #BritGrav15
- Umberto Lupo also thinking about black holes in a box http://arxiv.org/abs/1502.06582 Is there a description of thermal equilibrium? #BritGrav15
## Session 8 (Chair: Alberto Vecchio)

- 2014 Thesis Prize Winner Anna Heffernan
- First @PhysicsNews prize talk: Anna Heffernan, The Self-Force Problem #BritGrav15
- Announcement about Anna's prize here: http://cqgplus.com/tag/gpg-thesis-prize/ …
- Heffernan: Need self-force for extreme mass-ratio inspirals (EMRIs), a gravitational-wave source for eLISA! See http://rhcole.com/apps/GWplotter/
- Heffernan: Singular field doesn't look nice when written down, but makes some pretty plots! (Slide 28: http://www.sr.bham.ac.uk/britgrav15/slides/session8/02_AnnaHeffernanBritGrav15.pdf …)
- Heffernan: Need to be careful subtracted infinities. Will use mode-sum regularization with cunning coordinate choice. #BritGrav15
- Heffernan: Using this improvement in self-force calculations, others went on to investigate ISCO, etc. #BritGrav15
- Heffernan: Looked at effective source method as alternative to mode-sum. More pretty pictures on slide 56 ( http://www.sr.bham.ac.uk/britgrav15/slides/session8/02_AnnaHeffernanBritGrav15.pdf …)
- Heffernan: No EMRI waveforms as yet. Need more accurate Kerr results, 2nd order terms and orbit evolution. #BritGrav15
- Heffernan: Lots of thesis highlights. It went well! [Applause] #BritGrav15
- Dolan: Recent work on identifying gauge-invariant quantities instead of going directly for waveforms. #BritGrav15
- 2015 Thesis Prize Winner Patricia Schmidt
- This year's winner Patricia Schmidt: Modelling Precessing Black Hole Binaries. #BritGrav15
- Interview with Patricia Schmidt, 2015 GPG thesis prize winner http://wp.me/p47IEi-gg via @PublisherAD
- Schmidt: Want inspiral-merger-ringdown (IMR) waveforms for detection and parameter estimation in advanced detection era. #BritGrav15
- Schmidt: Tracking of orbital plane difficult in GR: use direction of dominant emission direction. #BritGrav15
- Schmidt: Have removed precession! Now use inverse procedure to make precessing waveforms: do the twist! #BritGrav15
- Schmidt: Over many precession cycles, can use average of spin. Checking match shows reduced spin parameters work. #BritGrav15
- Schmidt: End product is IMRPhenomP http://arxiv.org/abs/1308.3271 #BritGrav15
- Are we limited by lack of numerical waveforms to check against? Schmidt: Parameter space is huge. Work being done to explore. #BritGrav15
- Best Student Talk Prize
- #BritGrav15 best student talk prize sponsored by #CQG… Runners up Viraj Sanghai & Umberto Lupo. Winner: Christopher Moore! Congratulations!
- Thanks to John Miller, Carsten Gundlach & John @JohnVeitch for judging, and for @PublisherAD for the prize! #BritGrav15
- BritGrav 15 | BirminghamFollowing the close of the conference, we will be holding a public lecture. Prof. Jim Hough from the University of Glasgow's Institute for Gravitational Research will give a guest talk on the science of gravitational-wave detection and what to look forward to in 2015.